1. Field of the Invention
The present invention relates to an apparatus and method for aggregating and switching traffic in a subscriber network, and more particularly, to an apparatus and method for aggregating and switching traffic in a subscriber network, which can efficiently aggregate and switch subscriber traffic with various bandwidths in a broadband subscriber network where upstream traffic and downstream traffic are asymmetric.
2. Description of the Related Art
Major increases in Internet data transmission speeds have opened the way for the commercialization of various multimedia services, such as digital broadcasts, video-on-demand (VOD) services, video phone services, and video conferencing services. In order to provide, for example, Voice over Internet protocol (VoIP) services, broadcasting services, and other multimedia services together with existing data services, it is important to differentiate real-time traffic from other traffic and provide bandwidths to a plurality of subscribers while guaranteeing a high quality of service (QoS).
Conventional subscriber network technologies using telephone lines, such as xDSL and HFC, are only suitable for providing a bandwidth of 1-10 Mbps. Thus, it is necessary to develop new subscriber network technology that can provide higher bandwidths.
Recently, subscriber network technologies using Ethernet have been developed. These Ethernet-based subscriber network technologies are mainly used for establishing local area network (LAN) in businesses, and systems or devices implementing them are provided at lower costs than other Layer 2-related systems.
In addition, an increasing number of subscriber networks have been established using conventional Ethernet switches that are generally used to establish a fast Ethernet-based LAN. However, conventional Ethernet switches have been designed to serve a LAN and thus may not be suitable for processing subscriber traffic.
Subscriber traffic has a non-uniform distribution of destinations. In a subscriber network, in particular, almost no inter-subscriber traffic exists. In other words, a plurality of subscribers belonging to a subscriber network, unlike a plurality of users connected to a LAN, do not incur traffic thereamong because a subscriber network is not provided for enabling a plurality of subscribers therein to communicate but is provided for connecting the subscribers to an upper network. Accordingly, in a subscriber network, there are two important traffic flows, i.e., upstream traffic, which is traffic from a plurality of subscribers to an uplink, and downstream traffic, which is traffic from the uplink to the subscribers.
In addition, in a subscriber network, upstream traffic and downstream traffic are asymmetric, that is, the amount of downstream traffic is much larger than the amount of upstream traffic. It is important to process traffic that needs to be multicast, such as broadcast services. Even though the amount of upstream traffic is much smaller than the amount of downstream traffic, it is also important to transmit traffic in consideration of fairness among a plurality of subscribers who compete for the bandwidth of one uplink and the priority levels of the subscribers.
Conventional Ethernet switches used to establish an Ethernet-based subscriber network cannot fully reflect the general characteristics of a subscriber network described above. In other words, conventional Ethernet switches are designed to be suitable for a LAN with uniform and symmetric user traffic and thus may not be suitable for efficiently processing traffic in a subscriber network with asymmetric traffic.
For example, in order to form an Ethernet switch having N ports, an N×N switch fabric configuration is needed. However, given that there is little inter-subscriber traffic in a subscriber network, a switching capacity of only about (N ×1+1×N) is needed to accommodate N subscribers.
In addition, conventional Ethernet switches that are currently available commercially are designed to have a shared buffer or shared bus architecture. An example of a conventional Ethernet switch having a shared buffer or shared bus architecture has been presented by Michael V. Lan, et al., [“Gigabit Ethernet Switches Using a Shared Buffer Architecture”, IEEE Communications Magazine Vol. 41, Issue 12, pp. 76-84, December 2003].
As a number of ports in a conventional Ethernet switch having a shared buffer or shared bus architecture increases, an operating speed of a shared buffer or shared bus must increase accordingly, and this requirement makes it almost impossible to accommodate a considerable number of subscribers using a single device as specified by Nick McKeown [The iSLIP Scheduling Algorithm for Input-Queued Switches, IEEE/ACM Transactions on Networking, Vol. 7, pp. 188-201, April 1999].
In addition, in order to process multicast traffic, conventional Ethernet switches must duplicate a packet as many times as there are destinations to which the packet needs to be transmitted. Accordingly, in a case where multicast traffic having a high priority level, such as broadcast traffic, occupies most of the bandwidths available to a conventional Ethernet switch, the amount of resources that other traffic having lower priority levels can use may decrease considerably, and thus, the quality of data transmission may considerably deteriorate.